They do work, but . . . . Temperatures need to be up around 60 degrees for the nematodes to be active, and I've found that vine weevil grubs are active at lower temps than that. The adults are active for most of the year, and I find that a torchlight hunt is often effective. I have used Provado as a soil drench, and that seems to work well. I guess you're after something organic. As is always the way with organic methods, they are never a total cure. If they were, nature's natural balances would be too easily upset, and we'd be able to rule everything. Luckily, we can't, and I like that! Worthy

Nemesys vine weevil treatment is what you're thinking of - should really be used around late summer, early autumn, while the soil is still warm for best effect, but you can water them on around end of May or in June - not so effective, but better than nothing. You'll need to order on line - most garden centres don't stock this product because its live, and has a use by date. Otherwise its out there with a torch, as Worthy says - Provado is said to be effective, but I don't like to use it either because of its troublesome effects on bee colonies.

I've used Hydrangea leaves on the vinery floor, placed there late afternoon in late April and May, in the morning the adults are there and are easy to catch.

Another tip is to use a non peat based potting compost, they are not as fond of it as they are of peat. Also, with single stemmed plants, put a plastic/ lambswool/ tarred paper collar round the stem (as is done round cabbages to stop cabbage root fly). Cover the collar with at least 2 inches of fine grit. The adults lay their eggs on the stem of the plant where it enters the soil. If they cannot find that point then they go else where.